Recently, the development of artificial tubular organs has been energetically pushed forward to use them as a substitute for tubular organs such as blood vessels, tracheae and esophagi, and many clinical applications of such artificial organs have been reported in the medical field.
For the artificial tubular organs used as a substitute of tubular organs with a skeleton (cartilage) such as tracheae and bronchi, Belsey, R. has reported in British J. Surg. 38 200 (1950), clinical trials employing a stainless steel wire closely wound in the form of a helix and covered with a fascia, and Daniel, R. A et al have reported in Dis. Chest. 17 426 (1950) on experiments using a glass tube. These reports initiated the development of artificial tubular organs, and various investigations have been made on artificial tubular organs of a wide variety of materials.
In general, the requirements common to artificial tracheae are to have sufficient resistance to deformation, to cause no leakage of air, and to be incorporated into organisms without causing significant inflammatory response. To meet these requirements, many studies have been conducted on materials for artificial tracheae, and their structure. The most artificial tracheae of the prior art are in the form of meshes or solid tubes, but the investigations in recent years are directed to artificial organs composed of a supporting frame covered with a mesh such as woven fabrics or knitted goods.
In J. Thoracic & Cardovasc Surg. 72 525 (1976), Neville has stated the following six conditions are required for an ideal artificial trachea:
(1) to be airtight to avoid leakage of expired air and inspired air; PA0 (2) to have a suitable mechanical strength and resistance to deformation to avoid occlusion of the trachea by pressure; PA0 (3) to be taken in by the organism, PA0 (4) to be incorporated into the surrounding organisms with less inflammatory response; PA0 (5) to prevent fibroblasts from passing therethrough as well as to prevent bacteria from making an invasion into the lumen; and PA0 (6) to permit ingrowth of respiratory epithelia along the lumen. PA0 However, there is no artificial trachea which satisfies all these conditions, especially, the conditions (3), (4) and (6) simultaneously.
For example, the artificial tracheae as shown in FIGS. 9 and 10, known as arched grafts, involve a problem in the condition (3). Since such artificial tracheae generally comprise a mesh reinforced by a supporting frame 31 with a semicircular cross section shown in FIG. 9 or 10, they are poor in longitudinal extension and contraction. This causes abrasion or releasing from the surrounding tissue, resulting in failure to be taken in by the organism.
In Japanese patent national publication No. 2-501118, it has been proposed to use an artificial blood vessel comprising a medical prosthetic material of a tubular woven fabric constructed by alternately performing plain weave and twill weave. This artificial blood vessel is improved in softness and flexibility and may be used without performing coating of a coagulant. However, the softness is lost from the blood vessel by the adhesion with the surrounding tissues, so that the blood vessel cannot follow with the movement of the body, thus causing inflammation of the tissue.
Japanese patent lying-open No. 57-115250 discloses an artificial tubular organ coated with a blood coagulation factor XIII (or fibrin stabilizing factor), which is used as an artificial trachea to be implanted in a resected portion of the trachea invaded by cancer or in a resected portion of bronchus affected with a tumor. This artificial tubular organ causes no risks such as obstructive thrombus, formation of ulcer or stenochoria as the rate of organization just after implantation is improved by the blood coagulation factor XIII.
However, the woven fabric or knitted goods used as the medical prosthetic materials for artificial tubular organs have the following disadvantages. If the fabric has a low compactness, the prosthetic material possesses good softness, but it permits the internal air to pass there-through and then intrudes into the tissue, causing inflammation due to microbism. If the prosthetic material is composed of a woven or knitted fabric of a compact construction, or of a fabric provided with a coating to give good airtightness and watertightness, the artificial tubular organ becomes rigid, does not fit to the surrounding tissue, prevents invasion of endotheliums, and causes disturbances in the surrounding tissue.
Commercially available artificial tubular organs comprise a silicone wire closely wound in the form of a helix and covered with a fabric to prevent the leakage of expired air or inspired air. In such an artificial trachea, however, the granulation tissue is prevented from entering into the medical prosthetic material. Thus, the artificial trachea is prevented from incorporation into the surrounding tissue so that the migration of the artificial trachea occurs.